Washington (CNN) - Sen. Barbara Mikulski, D-Maryland, will step up to the helm of the Senate Appropriations committee, three Democratic sources told CNN, and one source said she would be the first woman to chair that powerful panel.

Her assignment to that committee comes after Sen. Patrick Leahy said earlier Wednesday he would not take the post. He chairs the Senate Judiciary Committee and became the most senior Democrat in the Senate after the death this week of Sen. Daniel Inouye of Hawaii, who previously chaired the Appropriations committee.- Follow the Ticker on Twitter: @PoliticalTicker

Sen. Dianne Feinstein, D-California, who was planning to take over the Judiciary Committee if Leahy vacated the chairman's job, will instead remain the chairman of Senate Select Committee on Intelligence, according to Feinstein who spoke to CNN.

Mikulski was among those considered a possible successor to Inouye's chair after Leahy declined. Others included the senior Sens. Tom Harkin of Iowa, and Patty Murray of Washington.